Nanotubes with conductive properties are cylindrical members with highly microscopic diameters of several to several tens of nanometers and significantly large aspect ratios of about 10˜1,000. Carriers are migrated by ballistic transport within a nanotube having a generally uniform resistance along its length. Particularly, a carbon nanotube has carrier mobility of about 70 times or more than that of silicon at a room temperature.
Because of excellent electrical characteristics, nanotubes can be applied to semiconductor devices, flat panel displays, batteries, various sensors, etc. Particularly, in a conventional nanotube semiconductor device, the nanotube is used as a channel through which carriers are migrated or is used as a lower electrode of a capacitor.
A bit line applied to a conventional nanotube semiconductor device can be fabricated to have a diameter of about several to several hundreds of nanometers. However, if the bit line of several to several hundreds of nanometers is fabricated in a typical manner that simply decreases a width of a conductive material, then grain boundary defects within the bit line may cut off electrical connection.